Gluster server needs a filesystem that supports extended attributes for its
data. Some distros (Debian, Ubuntu) ship Docker that runs containers on aufs,
which does not support extended attributes and therefore Gluster server fails
there.
We can use tmpfs for Gluster server data volumes instead of a directory inside
the container.
We can then avoid the following warning:
```
WARNING: The '--' argument must be specified between gcloud specific args on the left and DOCKER_ARGS on the right. IMPORTANT: previously, commands allowed the omission of the --, and unparsed arguments were treated as implementation args. This usage is being deprecated and will be removed in March 2017.
This will be strictly enforced in March 2017. Use 'gcloud beta docker' to see new behavior.
```
Signed-off-by: Jess Frazelle <acidburn@google.com>
Lucas Käldström